Both Think Secret and AppleInsider concur that Leopard is likely to be released on the final weekend of October.
Both sites pin the release of Mac OS X 10.5 Leopard on Friday 26th.
The date is reminiscent of the release of Mac OS X 10.4 Tiger back in 2005 when it was released on the last Friday of April at 6.00PM.
AppleInsider notes that none of its sources have ruled out Apple having more announcements up its sleeve in the last full week of October.
Leopard is yet to be declared Gold Master but recent builds have edged closer and are said to be release candidates. Going on Apple's past schedules the company has around 7-10 days before it must declare Golden Master and begin duplication.